Die holder member for use in cross head die apparatus

ABSTRACT

A novel die holder member for use in co-extrusion cross-head die apparatus for applying two coating materials in inner and outer layers to an electrical wire, or the like. A body member has a through, axial bore in which a tip and die members, with respective tip and die holders, are positioned. A pair of radial bores, with which sources of two flowable coating materials communicate, extend from the exterior of the body member to the axial bore. The first coating material flows forwardly of the apparatus through a first flow passage, the second coating material flows rearwardly through a second flow passage, and the two materials flow forwardly, in superposed relation, through a third flow passage from a confluence of the first and second passages to an orifice in the die member where they are deposited in uniform, inner and outer layers, on the wire. The die holder member of the invention has frustoconical external and internal surfaces with a first, annular groove extending to and 360° around the external surface. A second groove extends into and 180° around the external surface and communicates through grooves at each of its ends with the first groove. A plurality of spaced openings about the periphery of the first groove communicate between the first groove and the internal surface, whereby coating material deposited in the second groove flows into and around the first groove and through the openings therein to the interior of the die holder.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a division of application Ser. No.08/581,845, filed Jan. 2, 1996 now U.S. Pat. No. 5,665,164.

BACKGROUND OF THE INVENTION

The present invention relates to die holder members for use in dieassemblies of the cross-head type for applying coating materials to afilamentary member, e.g., plastic insulation to electrical wires. Morespecifically, the invention relates to novel and improved die holdermembers for use in co-extrusion, cross-head die apparatus forsimultaneously applying two layers of coating materials, i.e., an innerand an outer layer, to a filamentary member as it is movedlongitudinally through the apparatus.

Cross-head die assemblies, such as those disclosed in U.S. Pat. Nos.5,031,568 and 5,316,583 of the present inventor, include a body portionhaving a through, axial bore communicating with a radial bore. A tipmember, having a through bore for establishing the path of travel of thefilamentary member, is supported in the body axial bore by a tip holder,also referred to as a core tube. External surfaces on the tip and holdercooperate with internal surfaces on the die elements to define a flowpath for the coating material, which is heated in order to be in aflowable state. The flow path leads to a die orifice through which thefilamentary member and coating material pass as the coating layer isapplied.

It is sometimes necessary to apply two layers of coating material, onein covering relation to the other, to electrical wires, or the like.This may be accomplished by providing in the body portion two radialbores, through which sources of the two coating materials communicate atdifferent locations within the axial bore. It is difficult, however, toensure proper flow of the two materials through the die apparatus,providing the necessary symmetrical, coaxial coating layers.

It is a principal object of the present invention to provide a novel,die holder member for use in cross-head die apparatus for applying innerand outer layers of coating materials to a filamentary member in aunique manner, resulting in superior, double-layered coatings.

Another object is to provide a novel die holder member for use inco-extrusion, cross-head die apparatus which simplifies and facilitatesthe application of two, superposed layers of coating materials to afilamentary member.

Other objects will in part be obvious and will in part appearhereinafter.

SUMMARY OF THE INVENTION

The die apparatus wherein the die holder member of the invention isemployed comprises an assembly of elements including the usual bodymember with through, axial bore, a tip, tip holder (core tube), diemember and the die holder member of the present invention. Two radialbores in the body member communicate with the axial bore therein. Therear portion of the tip holder external surface is in mating engagementwith a portion of the interior surface of the body axial bore, and anannular groove, extending 360° around the tip holder is positionedinwardly adjacent one of the radial bores in the body. The annulargroove communicates through three axial grooves with a flow passageextending over the forward surface portion of the tip holder and thetip.

The die member having the orifice through which the coating materialsare extruded is matingly engaged on its external surface with the dieholder member of the present invention which in turn is matingly engagedwith the forward surface portion of the axial bore. A first annulargroove extends 180° about the external surface of the die holder and ispositioned with its midpoint inwardly adjacent the second radial bore inthe body member to receive the second coating material. The firstannular groove communicates at its ends with a second annular groove,positioned rearwardly of the first groove and extending 360° about thedie holder.

A succession of evenly spaced, small openings extend through the dieholder about the second annular groove. The second coating materialflows from the second radial bore into the first annular groove of thedie holder and thence into the second annular groove at diametricallyopposite positions. The second coating material flows entirely aroundthe second annular groove and through the openings therein into a flowpassage defined between an internal surface portion of the die holderand the external surface of a portion of the die member extendingrearwardly from the portion in mating engagement with the die holder.

The second coating material flows rearwardly of the apparatus for ashort distance before flowing forwardly through a flow passage common tothe first coating material defined between external surface portions ofthe tip holder and tip and the internal surface of the die member. Thesecond coating material flows through this passage in superposedrelation with the first coating material. It is in this relation thatthe two materials pass through the die orifice, coaxially surroundingthe filamentary member.

The foregoing and other features and advantages of the invention will bemore readily understood and fully appreciated from the followingdetailed description taken in conjunction with the accompanyingdrawings, which are now referred to.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of fully assembled cross-head die apparatusincorporating the die holder member of the present invention;

FIG. 2 is an exploded perspective view showing separately the elementsforming the apparatus of FIG. 1;

FIG. 3 is a side elevational view in full section on the line 3--3 ofFIG. 1;

FIG. 4 is an enlarged fragment of the circled portion of FIG. 3;

FIG. 5 is a perspective view of the body member of the apparatus;

FIG. 6 is a side elevational view in section on the line 6--6 of FIG. 5;

FIG. 7 is a perspective view of a retaining collar of the apparatus;

FIG. 8 is a side elevational view in section on the line 8--8 of FIG. 7;

FIG. 9 is a perspective view of the die holder member of the presentinvention;

FIG. 10 is a side elevational view on the line 10--10 of FIG. 9;

FIGS. 11, 12 and 13 are side, front and rear views, respectively, of thedie holder;

FIG. 14 is a perspective view of the die element;

FIG. 15 is a side elevational view on the line 15--15 of FIG. 14;

FIG. 16 is a perspective view of the tip element;

FIG. 17 is a side elevational view on the line 17--17 of FIG. 16;

FIG. 18 is a perspective view of the tip holder/core tube element of theapparatus;

FIG. 19 is a side elevational view in section on the line 19--19 of FIG.18;

FIG. 20 is a full side elevational view.of the tip holder, rotated 90°from the position of FIG. 19; and

FIGS. 21 and 22 are front and rear elevational views, respectively, seenfrom the positions indicated by lines 21--21 and 22--22 of FIG. 20.

DETAILED DESCRIPTION

The completely assembled cross-head die apparatus of the invention, asshown in FIGS. 1 and 3, is generally denoted by reference numeral 10.Individual components of apparatus 10, as seen more fully in FIG. 2, arecylindrical body member 12, front retaining collar 14, die holder 16,die member 18, tip 20, tip holder/core tube 22 and rear retaining nut24. Body member 12, shown individually in FIGS. 5 and 6 includesthrough, axial bore 26 with which first radial bore 28 and second radialbore 30 communicate. Radial bores 28 and 30 are internally threaded forconnection thereto in conventional fashion of respective sources offirst and second coating materials 32 and 34, respectively (FIGS. 3 and4). The coating materials are typically plastics suitable for theintended application, heated to a flowable condition. Front portion 36of body member 12 is externally threaded for engagement with internalthreads 38 of collar 14 (FIGS. 7 and 8).

Proceeding from front to rear, the next element of the assembly is dieholder 16, shown individually in FIGS. 9-13. Die holder 16 has afrustoconical external surface 40 extending between front and rear ends42 and 44, respectively, and a through, axial bore defined byfrustoconical, internal surface 46. First annular groove 48 extends 180°about external surface 40 and communicates at its ends through channels50 and 52 with second annular groove 54 which extends the full 360°about surface 40. A succession of evenly spaced openings 56 extendthrough the die member between groove 54 and internal surface 46. As anindication of relative dimensions, for a die holder having a bore withdiameters of 0.962" and 1.14" at its front and rear ends, respectively,groove 54 may be 0.18" in both width and depth with a total of thirtyfour openings 56, each having a diameter of 0.05".

Die member 18 has frustoconical external and internal surfaces 58 and60, respectively, the latter terminating at orifice 62 in front wall 64of the die member. External surface 58 extends from front wall 64 to arearward end 66. Portion 68 of the die member extends rearwardly fromend 66 of surface 58. External surface 70 of portion 68 is substantiallycylindrical, having a diameter d slightly less than the diameter D atend 66 of surface 58. Annular groove 72 extends entirely about the diemember at the forward end of portion 68.

Tip 20, as seen in FIGS. 16 and 17, has a through, axial bore 74 with adiameter slightly larger than that of the filamentary member to becoated by apparatus 10. The external surface of tip 20 is divided intotwo frustoconical portions, rear portion 76 diverging outwardly fromrear end 78 toward front end 80, and forward portion 82 converginginwardly from rear to front, terminating at the front end of bore 74.

The tip holder or core tube 22 is shown individually in FIGS. 18-22. Athrough, axial bore is defined by cylindrical, rear portion 84 andfrustoconical, forward portion 86. The external surface of tube 22includes cylindrical, externally threaded, rear portion 88, intermediateportion 90 diverging outwardly from rear to front, and forward portion92 converging inwardly from rear to front. Intermediate and forwardsurface portions 90 and 92 are separated by annular groove 94 whichextends fully about tube 22. Three axial grooves 96, 97 and 98 extendforwardly from annular groove 94 into forward surface portion 92. Asindicated in FIG. 21, axial groove 96 has a maximum width W which isgreater than the equal widths w of axial grooves 97 and 98. Themidpoints of axial grooves 97 and 98 are each spaced from the midpointof axial groove 96 by 100°, thus being spaced 160° from one another.Keyway 100 is formed in intermediate surface portion 90.

The manner of assembly of the elements and their physical relationshipsin the fully assembled condition are best understood with reference toFIGS. 2-4. Core tube 22 is inserted in axial bore 26 of body member 12from front to rear with intermediate portion 90 of the external surfaceof the tube in mating engagement with rear portion 26a (FIG. 6) of theinternal surface of bore 26. Rotational orientation of tube 22 relativeto body member 12 is established by key 102 (FIG. 3) extending intokeyway 100. Tube 22 is secured in position by tightening nut 24 uponportion 88 against the rear surface of body member 12. Annular groove 94is inwardly adjacent the inner end of first radial bore 28. The wider ofthe axial grooves in core tube 22, i.e., groove 96, is positioned 180°from the inner end of bore 28.

Tip 20 is inserted into the forward end of axial bore 86 of core tube22, either before or after insertion of the core tube in axial bore 26.Frustoconical surface 76 is angled for mating engagement with theforward portion of bore 86. Since tip 20 is symmetrical about itscentral axis, rotational orientation is of no consequence.

The forward end of die member 18 is inserted into the rearward end ofthe bore in die holder 16, placing surfaces 46 and 58 in matingengagement. Die holder 16 is then inserted into the forward end of axialbore 26, placing external surface 40 of the die holder in matingengagement with internal surface portion 26b of the axial bore in bodymember 12. Collar 14 is threaded onto portion 36 and tightened againstthe forward surface of body member 12 to secure die holder 16 in itsassembled position wherein the midpoint of annular groove 48 is inwardlyadjacent the inner end of second radial bore 30, completing assembly ofthe elements.

Filamentary member 104, assumed for purposes of present discussion to bean electrical wire, is moved from a supply roll (not shown) positionedrearwardly of apparatus 10, through cylindrical portion 84 of the borein core tube 22, bore 74 of tip 20 and orifice 62 of die member 18, andsecured to a winding station (not shown) a suitable distance forwardlyof the apparatus. As wire 104 is moved axially at a suitable speedthrough apparatus 10, a uniform, inner layer of first coating material32 is deposited on the wire and an outer layer of second coatingmaterial 34 is deposited in covering relation to the inner layer.

The nature of the coating operation is best understood with reference toFIG. 3 and the enlarged fragment thereof in FIG. 4. First coatingmaterial 32 flows through radial bore 28 into annular groove 94 causingit to flow around and fill groove 94, then flow forwardly of theapparatus, through axial grooves 96, 97 and 98, as well as through asmall (e.g., 0.015") clearance between bore 26 and the periphery of coretube 22 between the three axial grooves. Positioning wider groove 96180° opposite the inlet of material 32, with the two narrower grooves97, 98 on opposite sides with their midpoints each 80° from the midpointof the inlet, as well as providing the aforementioned clearance, ensuresan even distribution of material 32 about the established flow path.

Second coating material 34 flows from radial bore 30 into first annulargroove 48 of die holder 16. Since external surface 40 of the die holderis in mating engagement with opposing portions of surface 26b of bore 26both forwardly and rearwardly of groove 48, material 34 flows 90° ineach direction about groove 48 and through channels 50 and 52 intosecond annular groove 54. Material 34 flows 360° about groove 54 andthence radially inwardly through openings 56, into the annular spacebetween surface 70, including groove 72, of rear portion 68 of diemember 18 and the opposing portion of surface 26b of bore 26. As isevident from close inspection of FIG. 4, material 34 flows a shortdistance through this annular space in a direction rearwardly ofapparatus 10, as indicated by arrow 106, before reversing direction andflowing forwardly, in covering relation to the layer of first coatingmaterial 32. For clarity, two different types of stippling are used toillustrate first and second coating materials 32 and 34.

The path through which first coating material 32 is constrained to flowfrom its entry into bore 26, about annular groove 94, through axialgrooves 96, 97 and 98 and the clearance between core tube 22 and bore 26is termed a first flow path. Likewise, the path of second coatingmaterial 34 from radial bore 30 into annular groove 48, thence throughchannels 50 and 52 into annular groove 54, through openings 56 andrearwardly through the annular space between external surface 70 of rearportion 68 of die member 18 and the opposing surface of die holder 16 istermed a second flow path. The first and second flow paths merge at therearward end of die member 18 and both the first and second coatingmaterials flow through the third flow passageway, i.e., thefrustoconical space between external surface portions of core tube 22and tip 20, and internal surface 60 of die member 18 to orifice 62therein.

Throughout the third flow path, second material 34 remains in coveringrelation to first material 32, and it is in this relation that thematerials are applied as coatings to wire 104. After exiting apparatus10, materials 32 and 34 begin to cool and harden, and the coated wiremay be wound on a conventional spool a suitable distance forwardly ofapparatus 10.

What is claimed is:
 1. A die holder member for use in cross-head dieapparatus, said die holder member consisting of a unitary body membercomprising:a) front and rear ends in spaced, parallel, first and secondplanes, respectively; b) frustoconical, external and internal surfaceseach extending between said front and rear ends; c) an annular grooveextending into and 360° around said external surface and centered in athird plane, parallel to said first and second planes; and d) aplurality of spaced openings disposed within said groove andcommunicating between said groove and said internal surface.
 2. The dieholder of claim 1 wherein said third plane is closer to said first planethan to said second plane.
 3. The die holder of claim 1 wherein saidannular groove is substantially semi-circular in transverse crosssection and has a width approximately equal to its depth.
 4. The dieholder of claim 1 and further including a second groove extending intoand partially around said external surface between first and secondends, said second groove being axially spaced from said annular grooveand communicating therewith at each of said first and second ends. 5.The die holder of claim 4 wherein said second groove is centered in afourth plane parallel to and between said second and third planes. 6.The die holder of claim 5 wherein said annular groove and said secondgroove are substantially semi-circular in transverse cross section. 7.The die holder of claim 6 wherein the number of said openings is aboutthirty four.
 8. The die holder of claim 5 wherein said fourth plane iscloser to said first plane than to said second plane.
 9. The die holderof claim 8 wherein said die holder has a central, longitudinal axis andsaid openings extend radially with respect to said axis.